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Case Studies
Isthmic Spondylolisthesis with Spinal Stenosis
Kenneth L. Renkens, MD
Indianapolis Neurosurgical Group, Inc.

Case History
C.L. is a 44-year-old woman with a 2.5 year history of increasing left lower extremity pain. There was no history of trauma and her symptoms of left buttock and leg pain have been increasing in intensity. Walking and standing cause her pain to increase, while sitting and assuming a recumbent position decrease the pain. She has intermittent back pain but denies having any pain in her right leg. There are no problems with bowel, bladder, or sexual function. She works as a bank teller and does a lot of sitting.

The patient's past medical history is unremarkable. Her current medications include Ibuprofen and aspirin on a p.r.n. basis.

On physical examination she is a well-developed, well-nourished woman, alert and in no apparent distress when sitting in a chair. She has some discomfort in her left buttock and leg when transferring to the examining table. Examination of her back shows normal posture. She can forward flex 60°, then has some increase in pain in her left leg. She can hyperextend well without complaints of pain. Lateral flexion is performed normally. Straight leg raising is negative bilaterally. Motor examination of the lower extremities shows mild weakness in tibialis anterior and EHL on the left as well as mild quadriceps weakness, otherwise the motor examination in both lower extremities is normal. The sensory and reflex examinations are both normal. The reflex examination is normal. Range of motion of her hips and joints in the lower extremities does not reproduce her pain. The distal vascular exam is normal.

Complete imaging studies were done to evaluate her spine. A lateral view of the lumbar spine shows a grade 1 spondylolisthesis of L4 on L5 (Fig 1). Figure 2 is an AP view of the lumbosacral spine. A CT scan of the L4 area shows the spondylosis (Fig 3). Figure 4 is an MRI scan showing L4 nerve root compression in the foramen at the level of her spondylolysis and spondylolisthesis. Figure 5 is a midline sagittal MRI scan showing degeneration of the disc at the L4-5 level and normal disc hydration at L3-4 and L5-S1.

Fig. 1

Fig. 2

Fig. 3

Fig. 4

Fig. 5

Fig. 6

Fig. 7

(click on thumbnails)

Isthmic Spondylolisthesis: Discussion
Thomas G. Lowe, MD
University of Colorado School of Medicine, Denver, CO

This case illustrates the typical clinical and radiographic findings of isthmic spondylolisthesis associated with spinal stenosis. Although the patient does have mild mechanical low back pain, presumably related to the unstable spondylolisthetic segment and its degenerative disc, her major symptoms are related to the nerve root compression. Physical examination confirms both an L4 and L5 neurologic deficit on the right with a negative tension sign consistent with longstanding compressive radiculopathy at the L4-L5 level. The MRI reveals what appears to be a lateral disc protrusion at L4-5 creating foraminal stenosis and a desiccated disc at the same level on the T2 weighted images, with normal-appearing discs above and below. The midline sagital MRI also shows moderate central canal stenosis at the L4-L5 level. Flexion-extension lateral radiographs of the lumbar spine would have been helpful in evaluating the presence of translational instability of L4 on L5.

If non-operative treatment has not helped this patient, she has an excellent likelihood of improvement with surgical intervention. If a decompression alone is performed in adults with isthmic spondylolisthesis, even at a level with significant disc degeneration, further translation can occur producing recurrent radicular symptoms and new axial complaints. This is especially true at the L4-L5 level where progression even without surgery has not uncommonly been seen in adults.

I would offer the patient a combined L4-L5 decompression and fusion. Even though her symptoms are unilateral, I would recommend a central canal decompression and removal of disc material and any pars fibrocartilage impacting on the L4 and L5 nerve roots along with bilateral L4 foraminotomies. Following the decompression, I would cover the laminectomy defect with a free-fat graft. If there was less than 4 mm of translation at the L4-5 level, I would perform an uninstrumented L4-5 transverse process arthrodesis using autologous iliac bone. Certainly, a one-level uninstrumented fusion without significant instability or other risk factors carries a high success rate as long as autogenous iliac bone graft is used. If there was 4 mm or greater translation on stress radiographs or if the patient was a smoker, I would augment the fusion with pedicular instrumentation without any attempt at reduction of the spondylolisthesis.

Postoperatively, the patient must remain off nonsteroidal anti-inflammatory drugs for 6-8 weeks because of their possible negative effect on osteogenesis.

References
1. Daftari, TK: Nicotine in the revascularization of bone graft, an experimental study to rabbits. Spine April 15, 1994: 10(8): 904-911.

2 Jorgenson, SS, Lowe, TG. A prospective analysis of autugraft versus allograft in posterolateral lumbar fusion in the same patient. Spine. Sept 15, 1994:19(18); 2048-2053.

3. Osterman, K, Lindholm, TS. Late results of removal of the posterior element in the treatment of lytic spondylolisthesis. Clin. Ortho. 1976;117:121-128.

4. Wood, KB. Radiographic evaluation of instibility in spondylolisthesis. Spine. Aug 1 1994. 19(l5);1697-703.

5. Yuan, HA. A historical cohort study of pedicle screw fixation in thoracic, lumbar and sacral spinal fusions. Spine. Oct 15 1994;l9(20 Suppl) 22793-22965.

Isthmic Spondylolisthesis: Discussion
Carlos Villanueva, MD, PhD
Hospital VaIl d'Hebron, Barcelona, Spain

We are faced with a case of low degree isthmic spondylolisthesis at L4. Moderate pain began 2 years ago and the pattern is consistent with dynamic radiculopathy at L4. On physical exam there are minor, but not significant, motor changes, and no signs of radicular tension.

The MRI shows the typical bulging of annulus fibrosus with partial occupation of the foramen. None of the x-rays enable assessment of the patient's sagittal balance.

Typically, low-degree spondylolisthesis in adults first presents clinically as segmental instability when disc degeneration advances. But it also creates positive sagittal imbalance due to the loss of the segmental lordosis as well as the translational displacement of the listhesic vertebra.1

The treatment of this segmental instability was short in situ fusion, but the sagittal imbalance remains uncorrected, if not worse postoperatively. In patients like this, with a long life expectancy, we believe that complete restoration of all spinal physiologic parameters must be attempted.

The only way to reconstruct the listhetic segment is by restoration of the disc height and physiological segmental lordosis with a trapezoidal spacer that provides spontaneous reduction of the listhesis.2,3

Our proposal is: a posterior approach, laminectomy, bilateral radicular decompression, disc excision, and PLIF with two trapezoidal spacers (cages or ramps). The anterior arthrodesis needs to be stabilized by posterior pedicular instrumentation in compression and lordosis.5 Supplementary bilateral, lateral fusion is optional but recommended.4 Bone graft is taken from the ablated posterior arch and supplementary cancellous bone can be obtained from the iliac crest.

Complications of PLIF in young and middle-aged patients are rare. Some postoperative discomfort in the buttocks usually resolves spontaneously in two or three weeks. Disc space collapse is rare when vertebral end plates are respected. Postoperative fibrosis is also rare when proper techniques are used, however, significant postoperative leg pain of unknown cause remains in a small number of cases.

References
1. Bradford DS. In: Lonstein JE, Bradford DS, Winter RB, Ogilvie JW eds. Moe's textbook of schliosis and other spinal deformities. 3rd ed. Philadelphia, PA: WB Saunders; 1995.

2. Brantigan JW, Steffee, AD. A carbon fiber implant to aid interbody fusion. Two-year clinical results in the first 26 patients. Spine. 1993; 18(14):2106-7

3.Collins, JS. Total disc replacement: a modified posterior lumbar interbody fusion. Clin Orthop. 1985; 193: 64-67.

4. Kim, SS, Denis F. Lonstein JE, Winter RB. Factors affecting fusion reate in adult spondylolisthesis. Spine. 1990; 15:979-984.

5. Shirado O, Zdeblick T; Ward KE, McAfee PC. Biomechanical evaluation of posterior spinal stabilization methods for lumbosacral isthmic spondylolisthesis. Presented at 1990 annual meeting of AAOS, in New Orleans, LA.

Isthmic Spondylolisthesis with SpinaI stenosis:
Treatment and Follow-Up
Kenneth L. Renkens, MD

C.L. was treated with a posterior decompression of the L4 lamina and removal of the redundant synovium at the L4-5 level, decompressing the L4 roots. A lateral transverse process fusion was performed at L4-5 using iliac crest allograft bone. Segmental fixation using CD instrumentation was also performed at L4-5.

Four years after her decompression and fusion, the patient is back to all of her normal activities and is asymptomatic with regard to back or leg pain.

Figure 6 shows an AP of the lumbar spine showing good bony fusion opposite the L4-L5 transverse processes. Figure 7 shows the lateral view. No attempt was made to reduce the spondylolisthesis at the time of surgery.

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